.TH std::common_iterator::common_iterator 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::common_iterator::common_iterator \- std::common_iterator::common_iterator

.SH Synopsis
   constexpr common_iterator() requires std::default_initializable<I> \fB(1)\fP \fI(since C++20)\fP
   = default;
   constexpr common_iterator( I i );                                  \fB(2)\fP \fI(since C++20)\fP
   constexpr common_iterator( S s );                                  \fB(3)\fP \fI(since C++20)\fP
   template< class I2, class S2 >

   requires std::convertible_to<const I2&, I> &&                      \fB(4)\fP \fI(since C++20)\fP
            std::convertible_to<const S2&, S>

   constexpr common_iterator( const common_iterator<I2, S2>& x );

   Constructs a new iterator adaptor, effectively initializes the underlying
   std::variant<I, S> member object var to hold an I (iterator) or S (sentinel) object.

   1) Default constructor. Default-initializes var. After construction, var holds a
   value-initialized I object. Operations on the resulting iterator adaptor have
   defined behavior if and only if the corresponding operations on a value-initialized
   I also have defined behavior.
   2) After construction, var holds an I object move-constructed from i.
   3) After construction, var holds an S object move-constructed from s.
   4) After construction, var holds an I or S object initialized from the I2 or S2 held
   by x.var, if x.var holds that alternative, respectively. The behavior is undefined
   if x is in an invalid state, that is, x.var.valueless_by_exception() is equal to
   true.

.SH Parameters

   i - iterator to adapt
   s - sentinel to adapt
   x - iterator adaptor to copy

.SH Example


// Run this code

 #include <algorithm>
 #include <iostream>
 #include <iterator>
 #include <numeric>
 #include <vector>

 int main()
 {
     std::vector v{3, 1, 4, 1, 5, 9, 2};

     using CI = std::common_iterator<
                    std::counted_iterator<std::vector<int>::iterator>,
                    std::default_sentinel_t>;
     CI unused; // (1)
     CI start{std::counted_iterator{std::next(begin(v)), ssize(v) - 2}}; // (2)
     CI finish{std::default_sentinel}; // (3)
     CI first{start}; // (4)
     CI last{finish}; // (4)

     std::copy(first, last, std::ostream_iterator<int>{std::cout, " "});
     std::cout << '\\n';

     std::common_iterator<
         std::counted_iterator<
             std::ostream_iterator<double>>,
             std::default_sentinel_t>
             beg{std::counted_iterator{std::ostream_iterator<double>{std::cout,";  "}, 5}},
             end{std::default_sentinel};
     std::iota(beg, end, 3.1);
     std::cout << '\\n';
 }

.SH Output:

 1 4 1 5 9
 3.1;  4.1;  5.1;  6.1;  7.1;

.SH See also

   operator= assigns another iterator adaptor
   (C++20)   \fI(public member function)\fP
